Evidence for basolateral membrane potassium conductance in canine tracheal epithelium

The ionic dependence of the basolateral membrane conductance in canine tracheal epithelium was investigated using intracellular microelectrode techniques. Increasing the K+ concentration in the submucosal bathing solution depolarized the electrical potential difference across the basolateral membrane; neither alteration of the submucosal Na+ concentration nor the mucosal K+ concentration had a significant effect on the cellular electrical potential profile. An increase in the K+ concentration in the submucosal bathing solution also decreased the net rate of Cl-secretion. Addition of ouabain (10(-4) M) to the submucosal bathing solution decreased the short-circuit current and depolarized the intracellular voltage without altering transepithelial resistance or the cell membrane resistance ratio, suggesting that basolateral resistance was unchanged. These findings, together with the previous observation that there is no appreciable basolateral Cl- conductance, indicate that a K+ conductance accounts for the predominance of the electrical conductance at the basolateral membrane. The results also indicate that the basolateral membrane K+ conductance plays a critical role in the generation of the negative intracellular voltage that drives Cl- exit across the apical membrane and thus supports Cl- secretion.